BTEX removal from contaminated groundwater by a co‐culture of Pseudomonas putida and Pseudomonas fluorescens immobilized in a continuous fibrous‐bed bioreactor

A fibrous‐bed bioreactor with immobilized cells of Pseudomonas putida and Pseudomonas fluorescens was used to treat groundwater contaminated with benzene, toluene, ethylbenzene, and xylenes (collectively know as BTEX). The kinetics of BTEX biodegradation in the fibrous‐bed bioreactor operated under continuous well‐mixed conditions was studied at room temperature. Aeration was not used in the process fed with groundwater samples with an average total BTEX concentration of 2.75 mg dm^?3. All BTEX compounds present in the groundwater feed were concurrently and completely biodegraded even under oxygen‐limited or hypoxic conditions. Nearly 100% removal efficiency was obtained when the retention time was greater than 1 h. BTEX removal efficiency decreased with decreasing the retention time, with p‐ and o‐xylenes showed up first in the treated groundwater, followed by benzene and then other BTEX compounds. Biodegradation rates of BTEX generally increased with increasing BTEX concentration and loading rate. The maximum BTEX biodegradation rate was 5.76 mg h^?1 dm^?3 at the loading rate of 6.54 mg dm^?3 h^?1. The bioreactor had a stable performance, maintaining its ability for efficient BTEX degradation without requiring additional nutrients for more than 1 month. The good performance of the fibrous‐bed bioreactor was attributed to the high cell density (～15 g dm^?3 reactor volume) in the fibrous matrix. © 2002 Society of Chemical Industry     

Ammonium fumarate production by free or immobilised Rhizopus arrhizus in bench‐ and laboratory‐scale bioreactors

Ammonium fumarate production from glucose‐based media by Rhizopus arrhizus NRRL 1526 with mycelial growth controlled by phosphorus limitation exhibited mixed‐growth‐associated product formation kinetics, with growth‐associated production related to secondary mycelial growth only. The contribution of the primary mycelial growth phase was minimised by resorting to prolonged batch production using free mycelia under intermittent glucose feeding or repeated batch production using immobilised mycelia. The metabolic activity of free or immobilised mycelia was limited by fumarate accumulation or by oxygen diffusion phenomena, respectively. For batch cultures in a 15 dm³ stirred bioreactor the peripheral impeller speed (v_I) was increased from 1.88 to 3.3 m s^?1, and the fumarate yield coefficient on glucose increased from 0.25 ± 0.01 to 0.42 ± 0.02 g g^?1, while the malate yield coefficient on fumarate (Y_M/F) reduced from 0.46 ± 0.01 to 0.14 ± 0.01 g g^?1. With a net increase in the fumarate‐to‐malate ratio from 2 to 6.5, a v_I value of 3.3 m s^?1 gave the best fermentation performance and provided a basis for further scale‐up studies. © 2002 Society of Chemical Industry     

Assessing the reaction to fire of cables by a new bench‐scale method

The recently approved EU Construction Products Regulation (CPR) applies to cables as construction products. The difficulty of predicting the fire performance of cables with respect to propagation of flame and contribution to fire hazards is well known. The new standard EN 50399 describes a full‐scale test method for the classification of vertically mounted bunched cables according to CPR. Consideration of the material, time, and thus cost requires an alternative bench‐scale fire test, which finds strong demand for screening and development purposes. The development of such a bench‐scale fire test to assess the fire performance of multiple vertically mounted cables is described. A practical module for the cone calorimeter is proposed, simulating the fire scenario of the EN 50399 on the bench scale. The efficacy of this module in predicting full‐scale CPR test results is shown for a set of 20 different optical cables. Key properties such as peak heat release rate (PHRR), fire growth rate (FIGRA), and flame spread are linked to each other by factors of around 5. In a case study, the bench‐scale test designed was used to investigate the influence of the main components on the fire behaviour of a complex optical cable. Copyright © 2016 John Wiley & Sons, Ltd.     

Physiological comparison of Pseudomonas putida between two growth phases during cometabolism of 4‐chlorophenol in presence of phenol and glutamate: a proteomics approach

BACKGROUND: In cometabolic transformation of 4‐chlorophenol (4‐cp) in the presence of phenol and sodium glutamate (SG), a new biphasic growth pattern has been reported. This study investigates the physiological changes of Pseudomonas putida P8 during the biphasic growth by means of 2‐dimensional gel electrophoresis (2‐DE) and MALDI‐TOF analyses. RESULTS: A total of 49 protein spots were selected and identified in the 2‐DE gels from P. putida P8 grown on a mixed substrate containing 200 mg L^?1 of phenol, 200 mg L^?1 of 4‐cp and 1000 mg L^?1 SG. Among them, 16 protein spots were found differentially expressed in the two exponential growth phases during the biphasic growth, including six catabolic enzymes (DmpC, DmpD, DmpE, DmpF, DmpG and AspA) for substrate utilization. The expression of other proteins involved in detoxification and stress responses, carbohydrate and energy metabolism, and environmental information processing as well as a multifunctional xenobiotic reductase (XenA) was quantitatively analyzed and discussed. CONCLUSION: The expression levels of the identified catabolic enzymes during growth in the two growth phases correlated well with the substrate utilization patterns observed in previous kinetics studies. Furthermore, the results show that cells growing on a mixture of aromatic substrates undergo significant physiological changes. Copyright © 2009 Society of Chemical Industry     

Study on the dissolved oxygen control strategy in large‐scale vitamin B12 fermentation by Pseudomonas denitrificans

BACKGROUND: There are two different routes for vitamin B₁₂ biosynthesis, which results in discrepancies and uncertainties of the dissolved oxygen (DO) concentration for vitamin B₁₂ fermentation. In this paper, the DO control strategy was explored for industrial vitamin B₁₂ fermentation by Pesudomonas denitrificans in 120000‐L fermenter. RESULTS: A DO‐stat strategy was first successfully scaled up from a 9000 L fermenter to a 120 000 L fermenter. Then a multi‐stage DO control strategy was further established in the 120 000 L fermenter, in which the DO level was shifted from 8–10% (20–48 h) to 2–5% (49–106 h) and below 2% (107–168 h) by gradually reducing the rate of aeration and agitation. As a result, 198.80 mg L^?1 of vitamin B₁₂ was obtained, which was significantly higher than those obtained under the fermentations with one‐stage DO control. CONCLUSIONS: The comparatively low DO level was favorable for vitamin B₁₂ biosynthesis, but it would have an extremely negative effect on cell growth. Compared with the low DO level maintained at all times of the fermentation process, a multi‐stage DO control strategy could not only increase the biomass but also improve vitamin B₁₂ biosynthesis. Copyright © 2012 Society of Chemical Industry     

Simultaneous degradation of atrazine and simazine by a binary culture of Stenotrophomonas maltophilia and Arthrobacter sp. in a two‐stage biofilm reactor

BACKGROUND: The impact of mixtures of chloro‐triazinic herbicides, such as atrazine and simazine, on aquatic ecosystems is of environmental concern. To study their biodegradation under various operational conditions, a binary community comprising Stenotrophomonas maltophilia and Arthrobacter sp. attached to the porous support of a packed bed reactor, was evaluated. RESULTS: The genetic analysis of the two atrazine‐degrading strains revealed that genes atzA, atzB, atzC are present in both bacteria, but only S. maltophilia possess atzD. Thus, by cultivating Arthrobacter sp. on these herbicides, cyanuric acid accumulation was observed. When the binary community was cultivated in the biofilm reactor, at all the loading rates probed, both herbicides were entirely removed. However, complete biodegradation of cyanuric acid was not achieved. CONCLUSIONS: Even with a two‐stage reactor, cyanuric acid was only partially removed. This fact could be attributed to the absence, in the second stage, of an easily degradable energy source, required by S. maltophilia for the uptake and cometabolic degradation of the recalcitrant heterocyclic ring. Responding to differences in nutritional conditions prevailing at each reactor stage, local differences in species' predominance were clearly detected by microbiological and molecular biology methods. Copyright © 2010 Society of Chemical Industry     

Degradation of TNT,RDX, and HMX Explosive Wastewaters Using Zero‐Valent Iron Nanoparticles

The high‐energy explosives 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), and the high melting explosive octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) are common groundwater contaminants at active and abandoned munitions production facilities causing serious environmental problems. A highly efficient and environmentally friendly method was developed for the treatment of the explosives‐contaminated wastewaters using zero‐valent iron nanoparticles (ZVINs). ZVINs with diameters of 20–50 nm and specific surface areas of 42.56 m² g⁻¹ were synthesized by the co‐precipitation method. The explosives degradation reaction is expressed to be of pseudo first‐order and the kinetic reaction parameters are calculated based on different initial concentrations of TNT, RDX, and HMX. In addition, by comparison of the field emission scanning electron microscopy (FE‐SEM) images for the fresh and reacted ZVINs, it was apparent that the ZVINs were oxidized and aggregated to form Fe₃O₄ nanoparticles as a result of the chemical reaction. The X‐ray diffraction (XRD) and X‐ray absorption near edge structure (XANES) measurements confirmed that the ZVINs corrosion primarily occurred due to the formation of Fe₃O₄. Furthermore, the postulated reaction kinetics in different concentrations of TNT, RDX, and HMX, showed that the rate of TNT removal was higher than RDX and HMX. Furthermore, by‐products obtained after degradation of TNT (long‐chain alkanes/methylamine) and RDX/HMX (formaldehyde/methanol/hydrazine/dimethyl hydrazine) were determined by LC/MS/MS, respectively. The high reaction rate and significant removal efficiencies suggest that ZVINs might be suitable and powerful materials for an in‐situ degradation of explosive polluted wastewaters.     

Enhanced Cometabolic Transformation of 4‐Chlorophenol in the Presence of Phenol by Granular Activated Carbon Adsorption

Substrate inhibitions that manifest within the cometabolism system of 4‐chlorophenol (4‐cp) and phenol were alleviated through the application of granular activated carbon (GAC) in batch biodegradation. It was found that 4‐cp was preferentially adsorbed over phenol by the GAC and that 50% to 70% of the adsorption was achieved within the first two hours of contact. The kinetics of 4‐cp adsorption was also much faster than that of phenol, even when the co‐existing phenol was of a significantly higher initial concentration. As a result, competitive inhibition between the two compounds was minimized. Adsorption also caused a lowering of the phenol concentration in solution with a concomitant reduction in the substrate inhibition effect on cell growth. The addition of GAC benefited the biotransformation process through shortening the total degradation time for 600 mg L^?1 phenol and 100 mg L^?1 4‐cp from 42 h to 12 h; and it also made it possible for cells to survive and transform 600 mg L^?1 phenol and as high as 400 mg L^?1 4‐cp in free suspension cultures. Repeated operations in which GAC was reused showed that GAC could be regenerated by the cells, thus rendering the GAC incorporated process amenable to long term operations.     

Combined Effect of Agitation/Aeration and Fed‐Batch Strategy on Ubiquin‐ one‐10 Production by Pseudomonas diminuta

The effects of aeration rate and agitation speed on ubiquinone‐10 (CoQ10) submerged fermentation in a stirred‐tank reactor using Pseudomonas diminuta NCIM 2865 were investigated. CoQ10 production, biomass formation, glycerol utilization, and volumetric mass transfer coefficient (k_La) were affected by both aeration and agitation. An agitation speed of 400 rpm and aeration rate of 0.5 vvm supported the maximum production (38.56 mg L^–1) of CoQ10 during batch fermentation. The fermentation run supporting maximum production had an k_La of 27.07 h^–1 with the highest specific productivity and CoQ10 yield of 0.064 mg g^–1h^–1 and 0.96 mg g^–1 glycerol, respectively. Fermentation kinetics performed under optimum aeration and agitation showed the growth‐associated constant (a = 5.067 mg g^–1) to be higher than the nongrowth‐associated constant (β = 0.0242 mg g^–1h^–1). These results were successfully utilized for the development of fed‐batch fermentation, which increased the CoQ10 production from 38.56 mg L^–1 to 42.85 mg L^–1.     

One‐Pot Cascade Reactions using Fructose‐6‐phosphate Aldolase: Efficient Synthesis of D‐Arabinose 5‐Phosphate,D‐Fructose 6‐Phosphate and Analogues

One‐pot multienzymatic reactions have been performed for the synthesis of 1‐deoxy‐D ‐fructose 6‐phosphate, 1,2‐dideoxy‐D ‐arabino‐hept‐3‐ulose 7‐phosphate, D ‐fructose 6‐phosphate and D ‐arabinose 5‐phosphate. The whole synthetic strategy is based on an aldol addition reaction catalysed by fructose‐6‐phosphate aldolase (FSA) as a key step of a three or four enzymes‐catalysed cascade reaction. The four known donors for FSA – dihydroxyacetone (DHA), hydroxyacetone (HA), 1‐hydroxy‐2‐butanone (HB) and glycolaldehyde (GA) – were used with D ‐glyceraldehyde 3‐phosphate as acceptor substrate. The target phosphorylated sugars were obtained in good to excellent yields and high purity.     

Novel lipase isolated from a Pseudomonas strain and its application in the synthesis of S(+)‐2‐O‐benzylglycerol‐1‐acetate

Isolation of a novel microbial lipase (EC 3.1.1.3) having specific catalytic activity for the synthesis of optically pure 2‐O‐benzylglycerol‐1‐acetate, the building block for the preparation of many β‐blockers, phospholipase A2 inhibitors and other biologically active compounds was the aim of this investigation. A Pseudomonas (strain G6), recently isolated from soil, produced an extracellular lipase. SDS–PAGE analysis showed that the lipase protein was a hexamer. The molecular weight of the sub‐units of the lipase protein were 10, 19, 29, 30, 47 and 53. The catalytic activity of the lipase was exploited for the synthesis of 2‐O‐benzylglycerol‐1‐acetate from 2‐O‐benzylglycerol through transesterification using vinyl acetate as acylating agent. High selectivity of the lipase towards the monoacetate product was demonstrated. A 97% enantiomeric excess (ee) of S(+)‐2‐O‐benzylglycerol‐1‐acetate was obtained when the reaction was carried out at room temperature with shaking. The lipase was highly active in anhydrous organic microenvironments and in non‐polar organic solvents with log P values above 2.5. © 2002 Society of Chemical Industry     

A coupled population balance model and CFD approach for the simulation of mixing issues in lab‐scale and industrial bioreactors

Lab‐scale (70 L) and industrial scale (70 m³) aerated fermenters are simulated using a commercial computational fluid dynamics code. The model combines an Euler‐Euler approach for the two‐phase flow, a population balance model for biological adaptation to concentration gradients, and a kinetic model for biological reactions. Scale‐up at constant volumetric mass transfer coefficient is performed, leading to concentration gradients at the large scale. The results show that for a given concentration field and a given circulation time t_c, the population (physiological) state depends on the characteristic time of biological adaptation T_a. The population specific growth rate (T_a?t_c) is found independent of the spatial location and closely related to the volume average concentration. Oppositely, the population specific uptake rate (T_a～t_c) is spatially heterogeneous. The resulting local disequilibria between the uptake rate and the growth rate provide an explanation for the decreased performances of poorly macromixed industrial bioreactors. © 2013 American Institute of Chemical Engineers AIChE J, 60: 27–40, 2014     

Laboratory‐ and pilot plant‐scale study on the dehydration of cyclohexane by pervaporation

In this work, pervaporation is applied for the dehydration of industrial cyclohexane, used as a solvent and reaction medium in the manufacture of synthetic rubbers. Working with initial concentrations of water in cyclohexane within the range of 0.090–0.110 kg m^?3, an experimental study was performed (i) in the laboratory, using a radial cell with a membrane area of 0.0178 m²; and (ii) in a pilot plant located at the industrial site, with a plate‐and‐frame membrane module and a total membrane area of 3 m 2 . In both cases, the same pervaporation membrane, with a preferential flux of water, was used. The mass transfer coefficient was determined, together with its dependence on the hydrodynamic regime. The higher hydraulic resistance of the plate‐and‐frame module generated a pressure decrease that limited the feed velocity, thus increasing the mass transfer resistance of the pervaporation process in comparison with the bench‐scale system. Copyright © 2005 Society of Chemical Industry     

Properties of poly(AAc‐co‐HPMA‐cl‐EGDMA) hydrogel‐bound lipase of Pseudomonas aeruginosa MTCC‐4713 and its use in synthesis of methyl acrylate

Microbial lipases (E.C. 3.1.1.3) are preferred biocatalysts for the synthesis of esters in organic solvents. Various extracellular thermoalkaliphilic lipases have been reported from Pseudomonas sp. In the present study, a purified alkaline thermoalkalophilic extracellular lipase of Pseudomonas aeruginosa MTCC‐4713 was efficiently immobilized onto a synthetic poly(AAc‐co‐HPMA‐cl‐EGDMA) hydrogel by adsorption and the bound lipase was evaluated for its hydrolytic potential towards various p‐nitrophenyl acyl esters varying in their C‐chain lengths. The bound lipase showed optimal hydrolytic activity towards p‐nitrophenyl palmitate (p‐NPP) at pH 8.5 and temperature 45°C. The hydrolytic activity of the hydrogel‐bound lipase was markedly enhanced by the presence of Hg²⁺, Fe³⁺, and NH salt ions in that order. The hydrogel‐immobilized lipase (25 mg) was used to perform esterification in various n‐alkane(s) that resulted in ～ 84.9 mM of methyl acrylate at 45°C in n‐heptane under shaking (120 rpm) after 6 h, when methanol and acrylic acid were used in a ratio of 100 mM:100 mM, respectively. Addition of a molecular sieve (3Å × 1.5 mm) to the reaction system at a concentration of 100 mg/reaction vol (1 mL) resulted in a moderate enhancement in conversion of reactants into methyl acrylate (85.6 mM). During the repetitive esterification under optimum conditions, the hydrogel‐bound lipase produced 71.3 mM of ester after 10th cycle of reuse. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 183–191, 2007     

Preparation of conductive polyaniline/nylon‐6 composite films by polymerization of aniline in nylon‐6 matrix

Polyaniline (PANI)/Nylon‐6 composite films were prepared by oxidative polymerization of aniline (ANI) inside host Nylon‐6 film. Such a composite has the desired electro‐active and mechanical properties to serve as a self‐standing functional unit. Comparative studies on sorption of ANI by Nylon‐6 matrix from various ANI containing media were conducted revealing superior ANI uptake from neutral ANI solution in water. ANI content was measured to be as high as 12%. Spectroscopic measurements showed that hydrogen bonding seemed to play important role in ANI sorption by Nylon‐6 matrix. Polymerization was monitored using atomic force microscopy and conductivity measurements. The morphology studies showed the appearance of PANI nanodomains on Nylon‐6 surface in the early stages of the polymerization. Eventually the domains coalesced during polymerization forming a continuous PANI layer. The conductivity measurements confirmed the change of the morphology from isolated islands to continuous conducting surface by drastic increase in conductivity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Modular methanol manufacturing from shale gas: Techno‐economic and environmental analyses of conventional large‐scale production versus small‐scale distributed,modular processing

This article presents comparative techno‐economic and environmental analyses of four representative shale gas monetization options, namely, conventional shale gas processing, large‐scale methanol manufacturing, modular methanol manufacturing with shale gas supplied by pipelines, and modular methanol manufacturing with consideration of plant relocation. We first present shale gas supply models for the four gas monetization options. Next, the process designs for shale gas processing and methanol manufacturing from shale gas are described. We develop detailed process simulation models for shale gas processing and methanol manufacturing with different scales using raw shale gas extracted from the Marcellus, Eagle Ford, and Bakken shale plays. On this basis, techno‐economic analyses and environmental impact analyses are conducted for the four shale gas monetization options to systematically compare their economic and environmental performances based on the same conditions. The results show that modular methanol manufacturing is more economically competitive than conventional shale gas processing, although it leads to higher environmental impacts. Besides, modular methanol manufacturing is better than large‐scale methanol manufacturing for raw shale gas produced from distributed, remote wells from both economic and environmental perspectives. © 2017 American Institute of Chemical Engineers AIChE J, 64: 495–510, 2018     

Blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 toughened by maleated polystyrene‐based copolymers: Mechanical properties,morphology, and rheology

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6 30/70) blends were impact modified by addition of three kinds of maleated polystyrene‐based copolymers, i.e., maleated styrene‐ethylene‐butylene‐styrene copolymer (SEBS‐g‐MA), maleated methyl methacrylate‐butadiene‐styrene copolymer (MBS‐g‐MA), and maleated acrylonitrile‐butadiene‐styrene copolymer (ABS‐g‐MA). The mechanical properties, morphology and rheological behavior of the impact modified PPO/PA6 blends were investigated. The selective location of the maleated copolymers in one phase or at interface accounted for the different toughening effects of the maleated copolymer, which is closely related to their molecular structure and composition. SEBS‐g‐MA was uniformly dispersed in PPO phase and greatly toughened PPO/PA6 blends even at low temperature. MBS‐g‐MA particles were mainly dispersed in the PA6 phase and around the PPO phase, resulting in a significant enhancement of the notched Izod impact strength of PPO/PA6 blends from 45 J/m to 281 J/m at the MBS‐g‐MA content of 20 phr. In comparison, the ABS‐g‐MA was mainly dispersed in PA6 phase without much influencing the original mechanical properties of the PPO/PA6 blend. The different molecule structure and selective location of the maleated copolymers in the blends were reflected by the change of rheological behavior as well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010